Method for lubrication and for protection against corrosion, and aqueous colloidal compositions for performing this method



United States atent 3 ,3 7lfi47 Patented Feb. 27, 1968 Fice 3,371,047 METHOD F01! LUBRICATEQN AND FOR PROTEC- TION AGAINST CQRRQSIGN, AND AQUEOUS CGLLOIDAL CGMOSKTIONS FOR PERFORMENG THIS METHOD Henri Brunei, 9 Rue de General Niox, Paris 16, France No Drawing. Continuation-impart of application Ser. No. 203,095, June 18, 1962. This application July 29, 1965, Ser. No. 475,888

4 Claims. (Cl. 252-389) This invention relates to a method for protection of corrodible metal surfaces against corrosion as well as for the lubrication of said surfaces and to aqueous colloidal compositions required for this method.

These compositions are also useful as lubricants for metal parts, for metal tooling, cutting, and cooling and for uninfiammable hydraulic transmissions where they often give better results than hydrocarbon lubricants. They may be mixed with hydrocarbon lubricants in the form of very stable anticorrosive emulsions or with organic compounds having lubricating properties other than hydrocarbons for preparing aqueous anticorrosive lubricants for a great number of applications.

This application is a continuation-in-part of my US. application Ser. No. 203,005 filed June 18, 1962, now abandoned.

One of the most important problems concerning the protection of corrodible metals, for instance of ferrous metals (cast iron, steel and oxidable alloys) against rust, of copper and copper alloys against verdigris, of zinc against white rust, of magnesium against destructive oxidation, and so on, involves the temporary protection of rough-cast or tooled metal parts during the time which passes between their manufacturing and their utilization, for instance between the diverse Works and the diverse operations which aim at giving them their definitive form and, then when this definitive form is obtained, While Waiting for their final utilization, that is to say, in short, during all the period of storage and transportation. The paints and varnishes by means of which the finished metal objects are protected against corrosion cannot be applied to the metal before the fabrication of these objects has reached its final stage and, during the fabrication phases, it is current practice to provide for protection against corrosion by means of oils and greases essentially constituted of hydrocarbons in-which water-repellent products or corrosion inhibiting agents are often incorporated. The elimination of these oils and greases when one desires, later on, to Work or to paint the metal, requires, then, the use of organic solvents, special hot washes or detergents. Also, during the storage period, especially in open shelters, dust sticks to the greasy or oily surfaces which is not favorable to a good protection, dust often acting as small wicks for the penetration of moisture through the protective oil coating. In fact, experiments have demonstrated that the efiicacy of such means for protection of metals against corrosion is far from being absolute, especially in the case of a prolonged action of corrosion factors such as atmospheric humidity and sudden variations of temperature causing the condensation of atmospheric moisture. And it is frequently noticed, either when studying the phenomenon or in observations obtained from experience with storehouses, that, for example, the ferrous metal surfaces protected with hydrocarbon films, when they have been exposed a long time to an atmosphere saturated with moisture as it is the case in winter in nonheated rooms, present a tarnished or even burnished surface due to an oxide layer which seems to have developed below the oily film and which becomes apparent when this oily film is eliminated by means of a solvent. Furthermore, the oily lubricants used for lubricating, tooling or cutting of metals are different from the oils used as protective coatings on metals so that different products have to be supplied for each of these purposes. The most efficacious corrosion inhibiting agents, such as nitrites (for preventing the formation of rust on ferrous metals) or chromates (for preventing corrosion both of ferrous metals and of other corrodible metals), are water soluble salts insoluble in hydrocarbons so that it is not possible to introduce such inhibitors in a simple way in oils means for the protection of metals.

Among the objects of the invention is to provide a method for protecting, lubricating, tooling and cutting all types of metals by coating them with aqueous colloidal solutions which are possessed with strong anticorrosive properties not only for ferrous metals but for any corrodible metal.

Among other objects of the invention is to provide protective coatings for metal surfaces having a good mechanical resistance and strong anticorrosive properties.

Another object of the invention is to provide, with the same colloidal solution a single solution for lubricating and for forming a protective coating on metal surfaces which acts to protect the metal against corrosion when partial deterioration or dissolution of the coating of water occurs, or after rubbing contact in which the coating acts as a lubricant.

A still further object of the invention is to provide pro' tective coatings removable by water washing but so compounded that a protective film remains on the cleaned metal surface so that corrosion does not start immediately after washing.

A still further object of the invention is to provide protective coatings for metal surfaces which preserves them from any corrosion due to moisture or corrosive vapors and which are resistant by themselves to fermentations in presence of air and moisture.

A still further object of the invention is to provide a composition which imparts very good antifriction properties to metal surfaces lubricated therewith and which imparts cooling, cutting and protective properties to metals with the same aqueous lubricant composition.

A still further object of the invention is to simplify work in the metallurgy industry providing a single aqueous lubricant composition for lubricating during operations effected with machines on metal sheets, tubes or parts and for further protection of the same.

A still further feature of the invention is to provide protective coatings for metals which can be rendered water insoluble.

The percentages given in this weight unless otherwise specified.

The objects of the invention are attained by preparing an aqueous coating composition consisting essentially of three ingredients as follows: (1) a hydrophilic, neutral, mechanical resistant colloid which also is resistant to hydrolysis and coagulation, (2) a water soluble corrosion inhibitor for metals and (3) a water miscible or water soluble salt of a higher aliphatic or alicyclic amine which, per se, is insoluble or only slightly soluble in water and which has antiseptic and antifriction properties and also has hydrophobic film-forming properties for metal surfaces. The water content of the composition can vary over wide limits, and fillers, etc. may be added but these three essential components should be present in the proportion of 4060% of (1), 5-15% of (3) and 40-60% of (2) where (l)+(2)+(3)=100%.

The preferred hydrophilic colloids are the neutral starch ethers and particularly the hydroxy ethyl starch because of its availability and moderate cost. Other hydrophilic colloids which can be substituted for at least a portion of the starch ether include polyvinyl alcohol, casein, gelatin,

specification are by 3 etc. Other neutral starch ethers include methyl, ethyl, propyl starch, etc.

The water soluble corrosion inhibitors which can be employed include chromates formed by neutralizing chromic acid with alkali metal hydroxides or amines and the resinic complex formed from amine chromates in aqueous solution, borates formed by neutralizing boric acid with amines, the alkali metal or amine salts of mercaptobenzothiazole, the amine salts of hydroxy carboxylic and dicarboxylic acids such as lactic, tartaric, citric, oxalic, malonic, succinic, adipic, suberic and sebacic acids. Amines which may form the cations of the chromates, borates and organic acids include monoand dicyclohexylamines, mono-, di-, or triethanol and mono-, di-, or triisopropanol amines, ethylene diamine, diethylene triamine, dipropylene triamine, morpholine, etc. The amine salts of said acids also act as lubricants. Alkali metal nitrites and other known corrosion inhibitors may be employed in combination with these corrosion inhibitors.

The water miscible or water soluble salt of a higher aliphatic or alicyclic amine is a salt of an amine in which the alkyl or alicyclic group contains at least 6 carbon atoms. Such amines, per se, are water insoluble but when the salts thereof are prepared with formic, acetic, tartaric, lactic, citric, boric, hydrochloric, or nitric acids, said salts are water soluble. The lubricating properties of the compositions at least partially are attributable to these compounds.

A difficulty may arise when the chromic ion is added as a corrosion inhibitor since the chromic ion tends to precipitate the fatty amine salt. If the composition is made as described by first forming a colloidal solution of the starch ether and the fatty amine salt and only thereafter introducing the inhibitor solution containing the chromium ion, a homogeneous, stable, emulsion is obtained in which any fatty amine or salt thereof that is precipitated is in finely divided colloidal form.

Various additional materials may be added, depending on the use to which the composition will be put. Such additional ingredients include (a) various fillers such as paint pigments, finely ground mineral fillers such as metal oxides, talc, kaolin, (b) emulsifiable oils, (c) additional colloidal film forming ingredients such as sodium silicate, ((1) water soluble lubricating agents such as aminoalcohol salts of the hydroxy carboxylic acids and polycarboxylic acids set forth above, the polyalcohols, the polyepoxy glycols, etc.

The following examples will further illustrate various aspects of the invention and how the invention may be carried out in practice, but the invention is not restricted to these examples.

Example 1 50 kilograms of hydroxyethyl starch in fine grains are progressively dispersed in 950 kilograms of water, while agitating. After complete swelling of the colloid which may take a whole day at room temperature, but only a few hours at 50 C. and less than half an hour at 75 (3., there is obtained a viscous, opalescent, perfectly homogeneous, colloid solution to which there are incorporated, while agitating, 100 kilograms of a 10% aqueous solution of higher alkylaminopropylamine acetates derived from vegetable or animal fats and preferably from tallow. There is obtained a white fluid paste containing the water soluble acetate of water insoluble amines intimately emulsified in the colloidal solution. To this fluid paste, there are intimately mixed 100 kilograms of a concentrated aqueous solution of a water soluble corrosion inhibitor obtained by neutralizing 80 kilograms of a 50% aqueous solution of chromic acid with 70 kilograms of a caustic potash (potassium hydroxide) aqueous solution at 50% concentration, 10 kilograms of monocyclohexylamine or the corresponding amount of dicyclohexylamine and 25 kilograms of triethanolamine. There is obtained a greenish colloidal solution possessed with all the desirable properties set forth above and which may be applied as an anticorrosive lubricant for metal parts in work or in motion, as a cutting and cooling lubricant for metal tooling, as a noninflammable lubricating fluid for hydraulic transmissions or for hydraulic props or stanchions, as an anticorrosive cooling fluid for radiators or heat exchangers and as a water removable varnish for protection of metal surfaces against corrosion after applying and drying, the metal surface remaining temporarily protected against corrosion after removing the protective coating with water. This composition is not fermentable and the oily films obtained do not retain dust.

Example 2 In Example 1 there is mixed as the colloidal solution, instead of 1000 kilograms of aqueous solution containing 50 kilograms of hydroxy ethyl starch, 900 kilograms of the same colloidal solution of Example 1 in which 65 kilograms of triethanolamine are dissolved and then neutralized with 35 kilograms of boric acid in powder form while mixing until complete combination and until a homogeneous, viscous colloidal solution is obtained. Then the operations are followed as in Example 1 by incorporating the kilograms of an aqueous solution of alkylaminopropylamine acetate and the 100 kilograms of an aqueous solution of corrosion inhibitor. There is obtained a viscous colloidal solution suitable for applying on metal surfaces with a view to forming a dry film thereon which protects the metal against corrosion caused by humidity and chemical vapors. The films thus obtained show higher mechanical resistance than the films obtained with the compositions of Example 1 and, when dry, they form a smooth, transparent, green, varnish-like coating. This coating absorbs humidity and maintains-a high chemical anticorrosive potential in contact with metal surfaces and, when this potential decreases or is eliminated, it leaves a hydrophobic, water-repellent protective film on the surface of the metal which prolongs the protection against corrosion.

The viscous colloidal solution obtained in this example, when diluted with water to the desired concentration, constitutes an excellent lubricant having antifriction and cutting properties, utilizable especially for metal tooling and cutting, for example, when diluted with beween 2 and 3 times of its weight of water. Still higher dilution may be desired for grinding.

Example 3 In Examples 1 and 2, the water-soluble corrosion inhibitor set forth is replaced by triethanolarnine or triisopropanolamine chromate when the colloidal solution composition is not to be stored for long periods or transported over long distances.

Example 4 In Examples 1 or 2, the water soluble corrosion inhibitor is replaced by ethylene diamine, diethylene triamine, dipropylene triamine or morpholine chromate whereupon there is obtained a composition which is better for anticorrosive protection than for lubricating and cooling.

Example 5 or incorporated in the form of aqueoous solutions. The

cutting properties of the colloidal solutions thus obtained are less than when using the inhibitors of Examples 1 and 2.

, Example 6 In Examples 1 and 2, the water soluble corrosion inhibitor is partially replaced by the alkali-metal or triethanolarnine salt of mercaptobenzothiazole in proportion of l to 50% of the total inhibitor. This composition is especially effective when protecting, lubricating and tooling of copper or copper alloys is especially desired.

Example 7 In Example 2, the triethanolamine borate is replaced by mono or di or triethanolamine or mono or di or triisopropanolamine salts of an acid selected from lactic, tartaric or citric acid. This composition is especially effective when it is to be employed in lubricating and tooling and particularly in grinding operations.

Example 8 In Example 2, the triethanolamine borate is replaced by mono or di or triethanolamine or monor or di or triisopropanolamine salt of oxalic, malonic, succinic, adipic, suberic and/or sebacic acids. This composition is effective when it is to be applied for lubrication and cooling requiring high wetting properties. With adipic, suberic or sebacic acids, an antifroth agent is added to the colloidal anticorrosive solution so obtained. Silicone oil emulsified by the water soluble fatty amine salt of the composition is effective as an antifrothing agent.

Example 9 In Examples 1 or 2, the alkyl aminopropyl amine acetates are replaced by lauryl amine or a fatty amine derived from fatty acids other than lauric acid, for instance the fatty acids obtained by distilling when refining lauric acid and which have 14 to 16 carbon atoms, or oleic, palmitic, or stearic acid, or undecylenic acid obtained from castor oil.

Example 10 In Examples 1 or 2, the water soluble fatty amine salt is combined with the monoor dicyclohexylamine salt of the acids set forth in Examples 7 and 8, when protection of metals wrapped or stored in a small close-d space is aimed at.

Example 11 To the colloidal solution of any of the preceding examples there is added, to 65% of a filler such as powdered, water-insoluble, solid, neutral rocks, oxides and/or salts which may be white or colored, and the mixture is ground in a paint mill for a time sufiicient to provide a very fine dispersion of the filler (about a few microns in diameter) to provide aqueous anticorrosive colloidal paints which are removable with water and having all the properties of the anticorrosive colloidal solutions described above, but producing films which, after drying, are still more mechanically resistant providing perfect protection to the metal surfaces over long periods of time.

Example 12 Example 13 In Example 11, when water-soluble anticorrosive paints adapted to absorb radiations is desired, carbon black is added as at least a portion of said filler.

Example 14 To 450 kilograms of an aqueous colloidal solution containing 5% of hydroxyethyl starch prepared as in Example 1 there are added 32.5 kilograms of triethanol- 6 amine and then 17.5 kilograms of boric acid in powder form, while agitating. When the reaction is complete and the viscous liquid obtained is homogeneous, there are mixed 50 kilograms of the aqueous solution of alkyl amino propyl amine acetate as in Example 1 and, to the white, fluid paste obtained, there is incorporated 50 kilograms of the aqueous solution of the corrosion inhibitor of Example 1 and 50 kilograms of zinc chromate in powder form, 200 to 350 kilograms of talc in powder form, and to 200 kilograms of water according to the viscosity desired. The mixture is milled in a paint mill for the time necessary for obtaining the fineness desired in a paint. There are obtained about 1,000 kilograms of light yellow, water miscible, anticorrosive paint which forms mechanically resistant films removable with water.

Example 15 To a water miscible aqueous colloidal paint of Example 11 there are added, while milling, 5% of zinc chromate. There are obtained strongly anticorrosive, water miscible, colloidal paints giving resistant films removable with water.

Example 16 A drying hydrocarbon polymer such as the product known under the registered trademark CTLA polymer, is rendered emu-lsifiable in water by incorporating therein 3 to 20% of alkyl amino propyl amine acetate and then emulsified in proportion of 5 to 20% in the 5% aqueous colloidal solution or hydroxy ethy-l starch made as in Example 1. To the emulsion thus obtained, there are incorporated 5% of zinc or barium chromate in the form of a very fine powder. There is obtained a water miscible anticorrosive colloidal paint, which forms films that harden while drying due to the properties of the hydrocarbon polymer and which may produce under the action of heat, a hard coating utilizable as a primer. For accelerating the drying, 1 to 2% of cobalt naphthenate may be incorporated in the drying hydrocarbon polymer.

Example 17 When long duration protection of metal parts is desired, especially for shipping and storage in hot or cold damp climates, such as found in tropical countries or northern sea shores, the protective colloidal solutions according to the invention are combined with aqueous emulsions of elastomers. For example, to 100 kilograms of the colloidal anticorrosive solution of Examples 1 or 2, there are added 20 to 60 kilograms of an aqueous fine emu l sion of polyvinyl acetate containing 50% of water and plasticized by 5 to 10% of butyl phthalate. The mixture forms a colloidal emulsion analogous to a paint and by applying it on metal surfaces there is obtained a very neat and resistant film very adherent to the metal surface and which provides perfect protection against corrosion due to atmospheric humidity or sea fog for several months. The protective film thus obtained becomes practically insoluble in water, but when immersed under water for a certain time it separates from the metal and can be thus removed as a skin by peeling. After such removal, the metal surface remains nevertheless protected by the molecular hydrophobic and water-repellent film formed on the surface of the metal under the protective coating.

Example 18 For producing films by the invention, which are water insoluble when protection against rain or running water is desired, there is employed, as colloid, a polyvinyl alcohol or a mixture of polyvinyl alcohol and ether of starch, the rest of the preparation being unchanged. The water insolubility of the coatings resulting from the drying of the anticorrosive colloidal solutions according to the invention thus prepared is obtained by exposing said film to vapors of formaldehyde or by spraying with an aqueous solution of formaldehyde or of resorcin or of borax.

Example 19 In a Welded tube factory which makes use of the process (known in the art) which comprises first pickling of the iron strip in a bath of aqueous sulfuric acid, then washing in an aqueous neutralizing bath containing a caustic soda or potash Wash, then rinsing with water, then treating with neutralizing and dewatering 1 oil and then treating both the iron strip and the rollers for bending the same to tube shape with a lubricating oil, then electrically welding the two contacting edges to form the tube and finally spraying the tube after cooling with a protective oil before storage, all the lubricating and protecting coating products used after pickling and alkaline neutralization have been replaced by a colloidal solution of Example 1 or 2 and with this sole product a perfectly satisfactory result has been obtained for all operations which had previously necessitated at least three different products. In particular, the colloidal solution provides good lubrication during the formation of the tubes and does not hinder electric welding either under low or high voltage or by induction. Moreover, excellent protection during storage was obtained for the finished tubes coated with the colloidal solution.

Example 20 In spindle petroleum oil, preferably of the naphthenic type, there are dissolved to of the alkyl amino propyl amine acetate as set forth in Example 1. The spindle oil is thus rendered dispersible in water to give a White emulsion. This oil is emulsified in the proportion of 3 to 10% in an aqueous colloidal solution containing 5% of hydroxyethyl starch and, in the emulsion formed there is incorporated a water soluble corrosion inhibitor, for instance 3 to 10% of the corrosion inhibitor set forth in Example 1. There is obtained a strongly anticorrosive colloidal aqueous oil emulsion having high cooling and cutting properties and adapted to protect parts to be tooled against corrosion. Said emulsion may be diluted with water to varying degrees depending on the kind of work to be effected and the machine for effecting it.

Example 21 When hard films for protective coatings of metals are desired, there may be incorporated to the anticorrosive colloidal solutions made according to Example 1, 10 to 50% of 36 to 40 Baum sodium silicate aqueous solution. The viscosity of the colloidal solution is decreased by the addition but the viscosity is easily adjusted by adding hydroxy ethyl starch which swells rapidly in the fi-uidified solution. Instead, a more concentrated aqueous colloidal solution of the starch ether may be prepared originally to compensate for the decrease that will occur when the aqueous solution of sodium silicate is incorporated in the concentrated aqueous solution of the colloid. When dry, the protective films thus obtained are mechanically very resistant but remain nevertheless water removable.

Example 22 In above examples, the Water soluble acetate of waterinsoluble fatty amine is replaced by same amount of a chlorhydrate or of a nitrate of the same amines.

Example 23 In above examples the water soluble acetate of water insoluble fatty amine is replaced by a sulfate of the same 1 The term dcwatering is used in the metallurgy industry for eliminating Water on metal surfaces by immersion in waterrcpellant oils called dcwatering Oils.

Example 24 In Example 2, the triethanolamine borate is replaced or combined with a water soluble compound having lubricating properties selected from the water soluble polyalcohols and polycpoxy glycols, in the proportion of 2 to Example 25 The anticorrosive colloidal solutions of Examples 1 and 2 or the paints of Example 11, are evaporated or spray dried and the solid residue is converted to powder form to provide a powder which is soluble in Water and can be reconstituted to provide the original colloidal solution.

Example 26 a For reasons of economy or availability, part of the ether of starch is replaced as colloid in the above example by other cheaper colloids such as casein, gelatin, algina'tes, natural gums, products from the hydrolysis of starch such as dextrins, or polyvinyl alcohols.

I claim:

1. A composition for coating metal-surfaces and providing protection against corrosion and useful as an agent to aid in the machining, cutting and cooling of such metals comprising in combination as the essential ingredients in an aqueous colloidal solution,

40-50%, based on the total solid content, of a hydrophilic neutral colloid capable of forming films which are resistant to mechanical forces and consisting essentially of a starch ether,

40-60%, based on the total solids content, of a water soluble, corrosion-inhibiting salt selected from the group consisting of chromates of alkali metals and water soluble amines, borates of water soluble amines, salts of mercaptobenzothiazole with alkali metals and water soluble amines, and amine salts of lactic, tartaric, citric, oxalic, malonic, succinic, adipic, suberic and sebacic acids, said amines which provide the cations of said chromates, borates and aliphatic acids being selected from the group consisting of monoand dicyclohexylamines, mono-, di-, and triethanol and mono-, di-, and triisopropanol amines, ethylene diamine, diethylene triamine, dipropylene triamine and morpholine,

545%, based on the total solids content, of a water miscible salt of an amine selected from the group consisting of water-insoluble alicyclic and alkyl amines containing at least 6 carbon atoms and an acid selected from the group consisting of formic, acetic, tartaric, lactic, citric, boric, hydrochloric, and nitric acids.

2. A composition as claimed in claim 1 comprising in addition, at least one material selected from the group consisting of paint pigments, finely ground talc and finely ground kaolin in sufficient quantity to form a paint.

3. A composition as claimed in claim 1 wherein said starch ether is hydroxy ethyl starch.

4. A method of protecting a metal against corrosion and simultaneously imparting lubrication thereto comprising applying the composition as defined in claim 1 to a metal surface to provide a coherent, corrosion inhibiting film having lubricating properties which is removable by washing with water and provides pro tection against corrosion after washing with water.

References Cited UNITED STATES PATENTS Allen et a1. 106-14 Douty 106-237 X Kroenig et a1. 252-389 X Coleman et a1 106-14 Green et a1 252-75 Ulfstedt 206-14 X 10 3,019,195 1/1962 Denman et a1 252 3s9 3,046,230 7/1962 Berger 252-389 X 3,201,349 8/1965 Quantstrom 252-389 X FOREIGN PATENTS 5 509,765 2/1955 Canada.

648,765 1/1961 Great Bri rain.

LEON D. ROSDOL, Primary Examiner.

10 ALBERT T. MEYERS, SAMUEL H. BLECH,

Examiners. M. WEINBLATT, Assistant Examiner. 

1. A COMPOSITION FOR COATING METAL SURFACES AND PROVIDING PROTECTION AGAINST CORROSION AND USEFUL AS AN AGENT TO AID IN THE MACHINING, CUTTING AND COOLING OF SUCH METALS COMPRISING IN CIMBINATION AS THE ESSENTIAL INGREDIENTS IN AN AQUEOUS COLLOIDAL SOLUTION, 40-50%, BASED ON THE TOTAL SOLID CONTENT, OF A HYDROPHILIC NEUTRAL COLLOID CAPABLE OF FORMING FILMS WHICH ARE RESISTANT TO MECHANICAL FORCES AND CONSISTING ESSENTIALLY OF STARCH ETHER, 40-60%, BASED ON THE TOTAL SOLIDS CONTENT, OF A WATER SOLUBLE, CORROSION-INHIBITING SALT SELECTED FROM THE GROUP CONSISTING OF CHROMATES OF ALKALI METALS AND WATER SOLUBLE AMINES, BORATES OF WATER SOLUBLE AMINES, SALTS OF MERCAPTOBENZOTHIAZOLE WITH ALKALI METALS AND WATER SOLUBLE AMINES, AND AMINE SALTS OF LACTIC, TARTARIC, CITRIC, OXALIC, MALONIC, SUCCINIC, ADIPIC, SUBERIC AND SEBACIC ACIDS, SAID AMINES WHICH PROVIDE THE CATIONS OF SAID CHROMATES, BORATES AND ALIPHATIC ACIDS BEING SELECTED FROM THE GROUP CONSISTING OF MONO- AND DICYCLOHEXYLAMINES, MONO-, DI-, AND TRIETHANOL AND MONO-, DI-, AND TRIISOPROPANOL AMINES, ETHYLENE DIAMINE, DIETHYLENE TRIAMINE, DIPORPYLENE TRIAMINE AND MORPHOLINE, 5-15%, BASED ON THE TOTAL SOLIDS CONTENT, OF A WATER MISCIBLE SALT OF AN AMINE SELECTED FROM THE GROUP CONSISTING OF WATER-INSOLUBLE ALICYCLIC AND ALKYL AMINES CONTAINING AT LEAST 6 CARBON ATOMS AND AN ACID SELECTED FROM THE GROUP CONSISTING OF FORMIC, ACETIC, TARTARIC, LACTIC, CITRIC, BORIC, HYDROCHLORIC, AND NITRIC ACIDS. 